1. On the island of Ilios, red-tailed sea snakes consume frogs as their preferre
ID: 214235 • Letter: 1
Question
1. On the island of Ilios, red-tailed sea snakes consume frogs as their preferred prey. This predator-prey interaction demonstrates cyclic population cycles as described in the Lotka-Volterra models
A. (1) Which axis should be labeled “prey Population Size”?
B. (1) Which quadrant matches this description?
“Responding to a red algae bloom that killed most of the frogs, the red-tailed snake population also changes.”
C. (1) Which quadrant matches this description?
“Increasing snake fecundity has caused a change in frog population size”
D. (2) Use this model (frog/red-tailed snake) to explain coevolution.
IV Joint equilibrium pointExplanation / Answer
(a) The X-axis is Prey Population size. As we can see in the given graph, as the number of frogs increase, the number of snakes ( which feed off the frogs ) also increases. Eventually, the number of frogs starts decreasing ( quadrants 4 and 1) in response to increase in snake population.
(b) Quadrant 1 matches the description. The decrease in frog population directy causes a decrease in snake population due to scarcity of food. In quadrant 4, we see both frog and snake populations decrease.
(c) Quadrant 4 matches given description. As the snake population increases in number, the frog population decreases ( more preying ).
(d) The above graph can be split into 4 parts:
Quadrant 2: The initial population of both frogs and snakes is pretty low. As the frog number slowly starts increasing, the snake population still keeps decreasing due to low fecundity.
Quadrant 3: The frogs population keeps increasing, this means higher food supply for the snakes. In response, the snake population starts to increase.
Quadrant 4: Higher number of snakes causes the frog population to dwindle. The snake population though, keeps growing, due to high fecundity.
Quadrant 1: Decreasing number of frogs cause scarcity of food among snakes and hence, snake population starts decreasing.
The cycle repeats.
This very clearly exhibits coevolution, where two species which are linked ( in this case predator - prey ) directly influence the growth of one another.
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